Showing papers by "Academy of Sciences of the Czech Republic published in 1984"

Novel structural modulation in the first ambient-pressure sulfur-based organic superconductor (BEDT-TTF)2I3

Abstract: The compound bis(ethylenedithio)tetrathiofulvalene, or ET, is the first ambient-pressure sulfur-containing organic superconductor. It is further unique in having a displacively modulated structure below 200 K, which persists to at least 11 K. Important features of the room-temperature structure are the existence of ribbons of triodide anions and loose columnar stacks of ET molecules having intrastack S-S distances greater than 3.6 A, the sum of the van der Waals radii. The ET molecules are linked into infinite corrugated sheets by short interstack S-S distances less than 3.6 A and which lie approximately perpendicular to the ET molecule column-packing axis. These short interstack distances appear especially pertinent to the anisotropic (two-dimensional) electrical properties, which include a relatively high conductivity in directions parallel to the sheets. Crystal data was obtained by X-ray diffraction by use of the JANA program, which allows the description of the main and satellite intensities in a modulated structure in terms of one or more sinusoidal displacement waves with associated phases.

3-D analysis of LiNbO 3 : Ti channel waveguides and directional couplers

Abstract: An efficient method of calculation of effective refractive indexes and field distribution of guided optical modes in diffused channel waveguides and directional couplers is presented. Refractive index distribution which follows from the theory of two-dimensional anisotropic diffusion is considered. Experiments which relate the refractive index profile with fabrication parameters are described. Then the coupling length of a directional coupler can be calculated from the fabrication parameters. The results correspond well to recently published experimental data.

An Ohmic Contact Test Using the Activation Energy of Steady‐State Space‐Charge‐Limited Current

Abstract: The “visibility” of the Ohmic contact, which is usually tested by a simultaneous measurement of the dependence of current on voltage and on sample thickness is tested using the dependence of activation energy of the SCL current on applied voltage. The applicability of the method is illustrated on sandwich cells Au-metal-free phthalocyanine (H2Pc)-Au and SnO2-CdSe/H2Pc-(Al, Au) and c-Si(N+)-a-Si : H-Al heterostructures. Die „Sichtbarkeit” Ohmscher Kontakte, die gewohnlich durch simultane Messung der Abhangig-keit des Stromes von der Spannung und Probendicke getestet wird, wird mittels der Abhangigkeit der Aktivierungsenergie des SCL-Stromes von der angelegten Spannung uberpruft. Die Anwend-barkeit der Methode wird an Au-metallfreies Phthalozyanin (H2Pc)-Au-Sandwichzellen und SnO2-CdSe/H2Pc-(Al, Au)- und c-Si(N+)-a-Si : H-Al-Heterostrukturen uberpriift.

Optical and magnetooptical properties of Co-doped YIG films

Abstract: Analysis of cobalt contributions to the Faraday rotation spectra in the series of (YCa)3(FeCoGe)5O12 garnet films enabled us to distinguish between single contributions of Co2+ and Co3 ions in tetrahedral sites. It appeared that even the high counterdopes of calcium do not suppress the occurrence of tetrahedral Co2+ ions, although their concentration is greatly reduced in comparison with the original samples not containing any Ca. Noteworthy is also a rather high content of tetrahedral Co3+ in the samples not containing calcium even in cases when Ge content exceeds that of Co ions.

FMR linewidth and disorder in metals

Abstract: On discute de la contribution de l'interaction spin-orbite a l'amortissement de Landau-Lifshitz-Gilbert en termes de modele de liaisons fortes de Brooks et de l'approximation de Born pour un desordre diagonal de site

Contribution of Fe3+ ions to the growth induced anisotropy in garnet films

Abstract: Calcul de la contribution a l'anisotropie non cubique due a la distribution preferentielle des ions Fe 3+ . Examen particulier des couches minces de grenats contenant des ions Bi 3+ . Etude de quatre mecanismes differents pouvant expliquer les importantes anisotropies non cubiques de ces systemes. La modification de la decomposition en champ nul de Fe 3+ au second ordre induite par Bi 3+ est responsable de cette anisotropie

Nicotianamine, the ‘normalizing factor’ for the auxotroph tomato mutant Chloronerva ; a representative of a new class of plant effectors

Abstract: The article surveys our knowledge of the ‘normalizing factor’, gained from its discovery a quarter of a century ago up to the present time, under the following headings: Discovery; Physiological properties; Isolation and characterization; Structure determination (Identity of the ‘normalizing factor’ with nicotianamine); Chemical properties; Analysis; Synthesis; Occurrence and physiological role; Related compounds; Prospects.

The Λ c + production by 40–70 GeV neutrons on carbon

Abstract: The inclusive production of charmed baryonsΛ c + by 40–70 GeV neutrons on carbon has been observed. The decays $$\Lambda _c^ + \to \bar K^0 p\pi ^ + \pi ^ -$$ (130 ± 18 events) andΛ + →Λ 0π+π+π− (57±14 events) have been detected. The mean value ofΛ + mass is (2,268±6) MeV/c2. The invariant cross section forX>0.5 is described byE·d 3σ/dp 3∝ exp(−)bP T ·(1−X) n withb=(2.5±0.6) (GeV/c)−1 andn=(1.5±0.5). The cross section of theΛ + inclusive production measured forX>0.5 times the branching ratios are $$\sigma \cdot B(\bar K^0 p\pi ^ + \pi ^ - ) = (10 \pm 4)$$ μb per carbon nucleus and σ·B(Λ 0 π + π + π −)=(2.3±1.1) μb per carbon nucleus. The experiment has been performed in the neutron beam of the Serpukhov accelerator using the spectrometer BIS-2.

Central-peak—soft-mode coupling in ferroelectric Gd 2 Gd 2 ( MoO 4 ) 3

Abstract: Transmission measurements on ${\mathrm{Gd}}_{2}$ ${(\mathrm{M}\mathrm{o}{\mathrm{O}}_{4})}_{3}$ in the (5-50)-${\mathrm{cm}}^{\ensuremath{-}1}$ region were performed with use of tunable backward-wave oscillator sources (5-30 ${\mathrm{cm}}^{\ensuremath{-}1}$) and a Fourier spectrometer (30-50 ${\mathrm{cm}}^{\ensuremath{-}1}$). The resulting dielectric spectra show an additional low-frequency dispersion which was fitted with a standard central-peak model. Its characteristic relaxation frequency is \ensuremath{\sim}20 ${\mathrm{cm}}^{\ensuremath{-}1}$ and the coupling between the soft mode and central mode increases near the transition temperature. This model also accounts very well for the weak anomaly in the clamped permittivity ${\ensuremath{\epsilon}}_{c}$ measured at 63 MHz. The same central mode was used to fit earlier Raman soft-mode spectra. All of these data were fitted with a three-coupled-mode model which revealed that the soft-mode spectrum consists of two strongly coupled bare modes: a higher-frequency mode which softens and carries the entire Raman strength and a lower-frequency mode which is hard (59 ${\mathrm{cm}}^{\ensuremath{-}1}$) and Raman inactive. Both of these modes are also coupled to the central mode and this coupling increases sharply near the transition. The relatively large width of the central mode indicates its intrinsic nature and suggests partial disorder near the transition.

Spectral dependences of Faraday rotation in Y 3-x Bi x Fe 5 O 12 LPE films

Abstract: Spectral dependences of the Faraday rotation in a series of the bismuth substituted yttrium iron garnet LPE films are studied in the visible and near infrared region. It is found that in the 0.5 to 3.0 eV photon energy range the spectral dependence ef Faraday rotation in YIG can well be approached by nine paramagnetic and one diamagnetic transition types, respectively. On Bi substitutions only two additional paramagnetic transitions and changes in two other transitions already present in YIG are sufficient to explain the spectral behavior of the whole system. A method of determining Bi contents in rather thin LPE films and at low Bi concentrations is suggested.

Synthetic polymers as targetable carries for drugs

Abstract: The cellular phenomena of pinocytosis and lysosomal digestion are described, with particular emphasis on the handling of soluble macromolecules by living cells. A drug delivery system based on poly(hydroxypropylmethacrylamide) conjugated to drug analogues by oligopeptide sequences has been evaluated. The conjugates, which are stable in the bloodstream, are captured by pinocvtosis and taken to the lysosomal compartment of cells. There theoligopeptide sequences are hydrolysed by the lysosomal enzymes and the drug analogues released. Targeting has been demonstrated by incorporation into the polymer of side-chains bearing moieties that lead to non-specific or cellspecific adsorptive pinocytosis.

Correlation between Faraday rotation and bismuth and lead contents in LPE YIG films

Abstract: The main results of the present paper can be summarized as follows: a) By choosing suitable PbO-B2O3-Bi2O4 melts combined with appropriategrowth conditions it is possible to reduce significantly the content of lead atoms in garnet films leading to the incorporation of approx. 0·1 Pb per one Bi atom (y/x≈ ≈ 0·1). b) Account of the interference of the respective YL γ2,3, BiM α1 and PbM α1, PbM β1 X-ray lines in the EPMA method enables sufficiently exact determinations of Bi and Pb contents in garnet films. c) Determination of Bi contents in thin garnet films (1–2 μm) is made possible by measuring the FR near 500 nm. The magnitude of the minumum of the specific Faraday coefficient determines the Bi content and it has been shown that this value is not influenced by the presence of Pb ions.

Electron gas in discharge plasma in air

Abstract: We have presented a numerical solution of the electron Boltzmann equation in the two-terms approximation with given cross sections. The computations were performed for the electron gas in the dry air and a comparison with calculations in pure oxygen and nitrogen was made. Within the range of 2×10−17 −4×10−15 Vcm2 of the parameterE/N the mean kinetic energy of electrons, drift velocity, characteristic energy and transverse diffusion coefficient were calculated and compared with the available experimental data. Greater deviations of the electron swarm parameters from their experimental values were found in the dry air than in pure oxygen or nitrogen. We have been unable to identify the cause of these discrepancies, which exceed a likely error incurred by the use of the two-terms approximation [17]. For instance, in the present calculations the maximum deflection of the computedD T /μ from the experimental one in the case of dry air is about two times greater than in pure oxygen or nitrogen.

The Alternative Set Theory and its Approach to Cantor’s Set Theory

Abstract: This paper is compiled from articles of members of the Prague seminar on set theory. The first section is P.Vopěnka’s lecture at the occasion of Bolzano’s commemoration, Topological Symposium 1981, Prague; the second one was published in [So 1] and the third section is a part of the appendix of [v’]. For the last section we selected from many papers a series of mathematical results reached in the alternative set theory and the articles in question are cited in that section.

Observation and study of a narrow state in aΣ−(1,385)K+ system

Abstract: New data on the observation and study of a narrow resonance decaying intoΣ−(1,385)K+ have been obtained. The mass of the resonance is (1,956−6+8) MeV/c2, and its width is (27±15) MeV/c2. The resonance is produced in the diffraction dissociation of neutrons on quasi-free nucleons of carbon nuclei. The slope parameter of the differential cross section inPT2 is (9.9±3.0) (GeV/c)−2. The cross section times the branching ratio is (0.22±0.04) μb per nucleon. The resonance has one of the natural spinparities: 5/2+, 7/2− and so on.

Dielectric properties of SF6 mixtures containing oxygen and other gases

Abstract: This paper has explored the influence of an oxygen addition on the dielectric strength of the SF6 by numerically solving the Boltzmann equation with given cross section data. The linear variation of the dielectric strength with a mole fraction of oxygen was obtained. Similar calculations were performed for SF6 + air for which only approximative estimates had existed in the literature. To check the results and for other practical reasons the method of the Boltzmann equation was applied to the SF6 + He and SF6 + N2 mixtures, the dielectric strength of which had already been explored by other authors. In comparison with other mixtures currently studied the SF6 + O2 mixture reveals rather poor dielectric properties. In spite of the fact that the oxygen is an attaching gas, its addition to SF6 and its mixtures spoils the dielectric strength. This numerical analysis exactly qualified this behaviour and it is in agreement with the few available experiments.

Leukaemomycin‐geblockte Mutanten des Streptomyces griseus und ihre Pigmente II. Neue 7‐Hydroxy‐bisanhydro‐rhodomycinone aus der Mutante ZIMET 41707/1P

Abstract: Various blocked mutants were isolated from three leukaemomycin-(daunomycin-)producing strains IMET JA 3933, IMET JA 5142 and IMET JA 5570 of Streptomyces griseus by NTG and UV treatments. Among them, one class of four mutants ZIMET 43707/1P, IMET JA 5570/3P, IMET JA 5570/10P and IMET JA 5142/01P1 produced new blue and red pigments. Two red compounds designated 1PI and 1PII are the main components of the pigment complex produced by culture of the blocked mutant ZIMET 43707/1P. This paper describes the isolation of 1PI and IPII; furthermore, the spectral and physicochemical properties of these anthracyclinones and the elucidation of their structures are reported.

Physical kinetics of a hf glow discharge in oxygen. Generation of thea1 Δg state for pumping an iodine laser

Abstract: En partant de la fonction de distribution des electrons, la concentration de l'etat O 2 ( 1 Δ g ) dans un plasma actif est calculee dans l'hypothese ou la population de ce niveau n'est gouvernee que par les collisions electroniques. Le resultat semble indiquer que pour des valeurs realistes de l'intensite du champ effectif les concentrations accessibles de l'etat O 2 ( 1 Δ g ) sont trop faibles pour pouvoir pomper un laser a iode atomique par le transfert d'energie resonnant de l'oxygene excite a l'atome d'iode

Angular Dependence of SSWR in Thin Metallic Films Approximate Analytical Solution

Abstract: The spin-wave resonance spectrum characteristics, namely the mode position, linewidth, and intensity, for a thin homogeneous conducting film with an uniaxial surface anisotropy and an arbitrarily oriented external magnetic field are determined analytically using the spin-wave approximation. Comparison with the numerical data computed in the “full” model shows good agreement for all spin-wave modes including the lowest-order ones. Die Charakteristiken eines Spinwellenresonanzspektrums – Position, Linienbreite und Intensitat – in einer dunnen homogenen leitenden Schicht mit uniaxialer Oberflachenanisotropie und beliebig orientiertem auseren Magnetfeld werden analytisch mit Hilfe der Spinwellenapproximation abgeleitet. Der Vergleich mit den numerischen Daten, die fur das „Gesamtmodell” berechnet werden, zeigt eine gute Ubereinstimmung fur alle Spinwellenmoden einschlieslich die der niedrigsten Ordnungszahlen.